If you are sufficiently prepared, then we should begin. Let me explain the process to you.
I will begin by creating the basic summoning circle. When that is finished, my acolytes will use the rods of channeling to create the greater circle.

Once that is done, read the incantation from the Tome of the Cabal, and the felhunter will be pulled forth. Be careful, <name>. A felhunter is a powerful foe, and I'd like to see you keep your head on your shoulders.

Strahad will walk into the building he stands in front of, and a purple glyphed circle will be cast first, then a larger green glyphed circle. Use the Tome of the Cabal to summon the Felhunter you must fight and defeat. Having your Voidwalker already on-deck before starting the quest is a Good Thing®.

If you fail, you can abandon this quest and accept it again straight away from Strahad Farsan. Your old Tome of the Cabal will be destroyed, but do not worry. You get a new Tome when you re-accept the quest.